1. Field of the Invention
The present invention relates to a beamsplitter for splitting a light beam and including a plurality of reflecting surfaces arranged in a path of a collimated light beam and inclined to a propagation direction of the collimated light beam at an angle of 45.degree. for splitting the collimated light beam into a plurality of output beams extending perpendicular to each other. The present invention also relates to an optical alignment tool including the above-described beamsplitter.
2. Description of the Prior Art
In the constructional industry, optical devices, which are based on the use of luminous, collimated light beams, are replacing more and more the known since long ago, mechanical devices which provide, by using a visual control, for alignment and measurement of positional accuracy of constructional elements, built-in elements, installations and so forth. Since the time the semiconductor industry was able to provide a large number of laser diode capable of emitting light in the visible spectrum, usually red, a number of measuring devices, which replaced the previously known mechano-visual devices and which offered new measurement possibilities, found their application in the constructional industry. Thus, alignment tools, which are capable of emitting a collimated laser ray beam having a distance range up to about 20 m, a maximum diameter of about 10 mm, and a deviation from a horizontal propagation of about 1 mm per 10 m, have found a wide acceptance. In these tool, a horizontal alignment of the laser ray beam takes place, as a rule, automatically due to the influence of the gravitational force of the construction itself or due to the use of an appropriate control circuit.
In addition to a horizontal alignment and leveling, there exists a need in the constructional industry to determine plumb or to mark an exact right angle. U.S. Pat. No. 5,144,487 discloses a laser alignment device for performing the above-mentioned tasks. The known laser device is capable of emitting three laser ray beams lying in a common horizontal plane and extending at a right angle to each other. In addition, the tool emits also two plumb beams. To generate horizontal and plumb laser ray beams, a plurality of mirrors are arranged inside the tool and which deviate a primary laser ray beam, which is emitted by a laser diode, in the desired directions. The deviating mirrors, which produce altogether five horizontal and plumb beams, are arranged in a path of the primary laser ray beam in a spaced relationship to each other. Because of the mirror arrangement, the three-dimensional system of coordinates, which is formed by the emitted laser ray beams, has a zero point displacement or error. This is because the horizontal beams and the plumb beams have different virtual origins. Up to the present, the manufacturers of such laser devices dealt with this problem by providing constructively for a zero point displacement of about 20 mm. This zero point displacement or error should be taken into account when effecting measurements with the known laser devices. During the use of these laser devices, failure to take the zero point error into account presents a not insignificant source of an erroneous measurement. Further, the mirrors for forming output beams from the primary laser ray beam need be precisely aligned which makes the assembly of the device rather difficult. In addition, the arrangement of separate mirrors is rather sensitive to shocks which presents a serious drawback, in particular when the device is used on a constructional site.
Accordingly, an object of the present invention is a beamsplitter for splitting a primary light beam in a plurality of separate beams without a zero point error of the separate beams.
Another object of the present invention is a beamsplitter which could be easily mounted in an optical alignment tool, in particular, in a laser alignment tool.
A further object of the present invention is a beamsplitter having a rigid construction and capable of being used on a constructional site.